The present invention is directed to systems for detecting target ions in body fluids.
There is a clinical need for detecting target ions in body fluids such as blood, plasma, urine, and spinal fluid. Among the ions that are commonly detected are Ca.sup.++, Na.sup.+, and Cl-. One device used for detecting ions is an electrode, which produces a measurable electrical change upon contact with a fluid sample containing target ions.
Another device used for detecting ions is a thin film ion specific optode. These optodes contain a target ionophore which complexes with the target ion when present, and an indicator ionophore which provides an indication of such complexing, such as by a color change.
One problem associated with both of these devices is that they are incompatible with commonly used techniques for detecting organic compounds in body fluids. Organic components typically are detected using a photometric system where reagents are combined with a sample of the body fluid utilizing a pipette delivery system, and then the reagents are discarded after use. Contrarily, electrodes and thin film optodes are brought into contact with the sample, cleaned and then reused. Accordingly, clinical diagnostic equipment requires two different systems, one disposable, flowable reagent-based, and the other based on reused devices. This raises the cost of clinical diagnostic equipment because two independent measurement systems and the related hardware need to be combined in a single piece of equipment.
Another difficulty with conventional ion detection systems is the need to repeatedly clean the detection device after each use, which adds to the expense of the diagnostic process.
A third problem associated with conventional ion detector systems is that only low affinity ionophores can be used, because of the need to wash out the target ions from the electrode or optode after each use, so that the electrode or optode can be used for a new sample. If a high affinity ionophore is used, difficulty is experienced in washing out the target ion, with the result of lower throughput rates through an instrument.
Accordingly, there is a need for a method for detecting a target ion in a sample of a body fluid which can utilize equipment compatible with that used for analyzing organic compounds present in the body fluid, that does not require constant washing, and that can be used with high affinity ionophores.